The present invention relates to an amplifier arrangement. Similar amplifier arrangements are already known in the art, such as "Average efficiency of class-G power amplifiers", written by F. H. Raab, IEEE Transactions on Consumer Electronics, Vol CB-32, Nr May 2, 1986. Therein, class-G power amplifiers are described, including a first amplifier stage powered by a first couple of power supplies, and a second amplifier stage biased by a second couple of power supplies, the absolute value of the voltages delivered by this second couple of power supplies exceeding those of the first couple of power supplies. The output terminals of both amplifiers are coupled together and constitute the output terminal of the class-G amplifier arrangement. Furthermore, as can be observed from FIG. 1 of this prior art article, this class-G power amplifier includes a drive control, which includes an input terminal coupled to the input terminal of the amplifier arrangement, and which includes four output terminals, two of which are coupled to two input terminals of the first amplifier stage, another two of which are coupled to two input terminals of the second amplifier stage. The function of the prior art drive control is to make sure that input signals whose peak amplitudes are between the first and second supply voltages as delivered by the first couple of power supplies, are amplified exclusively by the first amplifier, as is stated in the introductory part of the prior art article, and that for signals of larger amplitude, the drive, which corresponds to the input signal, is switched from the first amplifier to the second one.
Furthermore, as is also further mentioned in this and other prior art documents concerned with class G amplifiers, the amplifiers included in such prior art amplifier arrangements, consist of amplifiers with an emitter follower or source follower transistor configuration. As is well known by a person skilled in the art, such emitter followers have a very low output impedance and a high current amplification, both items being excellent for high current driving of a load.
Yet emitter followers have a very low voltage gain. When such class-amplifiers are used as an output stage of for instance a line driver amplifier configuration, the complete voltage gain of this amplifier configuration is to be provided by the input or pre-amplifier, which precedes the class-G amplifier. Since this pre-amplifier, as a consequence, also has to provide the complete output signal swing, this pre-amplifier is to be supplied by the higher voltage power supplies. This of course increases the current consumption of this preamplifier, while at the same time reducing its linearity.